The conditional structure if is one of the fundamental concepts in programming, not only in Java, but in almost all programming languages. It allows a program to execute certain instructions based on the evaluation of a Boolean condition, that is, an expression that can be true (true) or false (false).< /p>
In its simplest form, a if statement in Java has the following syntax:
if (condition) {
// block of code to be executed if the condition is true
}
If the condition evaluated inside the parentheses is true, the associated block of code, delimited by the braces, will be executed. Otherwise, the program will continue execution to the next statement after the if block.
A common extension of the if statement is the use of else, which allows you to define a block of code to be executed if the if is not true. The syntax is as follows:
if (condition) {
// block of code to be executed if the condition is true
} else {
// block of code to be executed if the condition is false
}
In addition, it is possible to chain multiple conditions using the else if clause, thus creating a chain of conditional checks:
if (condition1) {
// block of code to be executed if condition1 is true
} else if (condition2) {
// block of code to be executed if condition2 is true
} else {
// block of code to be executed if none of the previous conditions are true
}
Another important conditional structure in Java is the switch. Unlike if, which can evaluate a wide range of true or false conditions, switch is used to compare a single variable with a series of constant values, known as cases (case). The basic syntax of switch is as follows:
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switch (variable) {
case value1:
// code block to be executed if variable == value1
break;
case value2:
// code block to be executed if variable == value2
break;
// ...
default:
// block of code to be executed if none of the previous case matches are true
}
It is important to note the use of the break keyword at the end of each case. break is used to end execution within the switch block and prevent the program from continuing to test subsequent cases. The default clause is optional and serves as a kind of "else" for the switch, being executed when none of the cases match the value of the variable.
As for loops, Java provides several structures to perform repetitions, that is, to execute a block of code several times. The most common loops are for, while and do-while. The for loop is generally used when the number of iterations is known in advance:
for (initialization; condition; increment) {
// block of code to be repeated
}
The while loop, on the other hand, executes a block of code as long as a condition is true and is more suitable when the number of iterations is not known in advance:
while (condition) {
// block of code to be repeated
}
Finally, the do-while loop is similar to while, but ensures that the code block is executed at least once, as the condition is evaluated after block execution:
do {
// block of code to be repeated
} while (condition);
Understanding these control flow structures is essential for any programmer, as they are the basis for creating programs that can make decisions and perform repetitive tasks. In Java, mastery of these structures allows the developer to create complex and efficient programs capable of dealing with a variety of scenarios and conditions.
